/*
 * FIPS 186-2 PRF for libcrypto
 * Copyright (c) 2004-2005, Jouni Malinen <j@w1.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 */

#include "includes.h"
#include <openssl/sha.h>

#include "common.h"
#include "crypto.h"


static void sha1_transform(u8 *state, const u8 data[64])
{
    SHA_CTX context;
    os_memset(&context, 0, sizeof(context));
    os_memcpy(&context.h0, state, 5 * 4);
    SHA1_Transform(&context, data);
    os_memcpy(state, &context.h0, 5 * 4);
}


int fips186_2_prf(const u8 *seed, size_t seed_len, u8 *x, size_t xlen)
{
    u8 xkey[64];
    u32 t[5], _t[5];
    int i, j, m, k;
    u8 *xpos = x;
    u32 carry;

    if (seed_len > sizeof(xkey))
        seed_len = sizeof(xkey);

    /* FIPS 186-2 + change notice 1 */

    os_memcpy(xkey, seed, seed_len);
    os_memset(xkey + seed_len, 0, 64 - seed_len);
    t[0] = 0x67452301;
    t[1] = 0xEFCDAB89;
    t[2] = 0x98BADCFE;
    t[3] = 0x10325476;
    t[4] = 0xC3D2E1F0;

    m = xlen / 40;
    for (j = 0; j < m; j++) {
        /* XSEED_j = 0 */
        for (i = 0; i < 2; i++) {
            /* XVAL = (XKEY + XSEED_j) mod 2^b */

            /* w_i = G(t, XVAL) */
            os_memcpy(_t, t, 20);
            sha1_transform((u8 *) _t, xkey);
            _t[0] = host_to_be32(_t[0]);
            _t[1] = host_to_be32(_t[1]);
            _t[2] = host_to_be32(_t[2]);
            _t[3] = host_to_be32(_t[3]);
            _t[4] = host_to_be32(_t[4]);
            os_memcpy(xpos, _t, 20);

            /* XKEY = (1 + XKEY + w_i) mod 2^b */
            carry = 1;
            for (k = 19; k >= 0; k--) {
                carry += xkey[k] + xpos[k];
                xkey[k] = carry & 0xff;
                carry >>= 8;
            }

            xpos += 20;
        }
        /* x_j = w_0|w_1 */
    }

    return 0;
}
